Mid-summer is the first opportunity for use to get some idea of what we might expect in terms of El Niño or La Niña effects on our upcoming winter. Well the prognosticators have weighed and the answer is - neutral!

Earlier this summer, the Climate Prediction Center/NCEP/NWSand the International Research Institute for Climate and Society folks had predicted a neutral year with neither an El Niño or La Niña event. Well things have changed and we are now under a La Niña watch. Here is the report:

A majority of the models in the IRI/CPC suite of Niño-3.4 predictions favor ENSO-neutral through the Northern Hemisphere 2017-18 winter [Fig. 6]. However, the most recent predictions from the NCEP Climate Forecast System (CFSv2) and the North American Multi-Model Ensemble (NMME) indicate the formation of La Niña as soon as the Northern Hemisphere fall 2017 [Fig. 7]. Forecasters favor these predictions in part because of the recent cooling of surface and sub-surface temperature anomalies, and also because of the higher degree of forecast skill at this time of year. In summary, there is an increasing chance (~55-60%) of La Niña during the Northern Hemisphere fall and winter 2017-18 (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

The past few La Niña events have caused atmospheric rivers to become more intense and has brought a lot of moisture to the Western United States. For those who forgot, last year was a La Niña:

I certainly don't want the drought to start up again, but the rains definitely did a lot of damage around here. The roads have suffered a lot because of the extremes of the soil. In the middle of the rains the ground swelled a great deal and now with the very hot and dry summer, the ground has contracted to another extreme. California rode out last winter mostly in stride, but our luck might not hold out if we get battered by a series of atmospheric rivers again.

I sure wish moderation would once more return to "climatological fashion."

The CLIMATE PREDICTION CENTER/NCEP/NWS and the International Research Institute for Climate and Society have updated their El Niño /La Niña predictions and we continue to be under a La Niña watch. Here is the full briefing:

This is further bolstered by the puzzling technical jargon to be found in the discussion for the first storm expected for this year on Thursday. The offending sentence reads as follows (key text with my emphasis) :

"IVT progs are focusing on Thursday evening being the best shot for moderate rainfall (coverage has decreased, but a narrow band of values over 500 KG/m/s are now indicated)."

To those who forgot from last year - IVT stands for Integrated Water Vapor Transport and Kg/m/s is a measure of how much water vapor is being transported. In other words, by decoding the technical jargon, it is clear that there was already the possibility for an atmospheric river event this early in October. The forecast has since downgraded the potential rainfall, but those of you in harm's way of atmospheric rivers might want to start preparing . . . . . just in case! . . .

. . . Well if you are going to all that trouble, perhaps you should "supersize" the Biblical dimensions for your ark, since it seems that we have identified quite a few more species than the Old Testament would have suggested. You also probably need all your binary math skills you can muster so you count all those animals one and then two to make sure you have a pair!! . . . .

" During October, weak La Niña conditions emerged as reflected by below-average sea surface temperatures (SSTs) across most of the central and eastern equatorial Pacific Ocean.

. . . .

For the remainder of the Northern Hemisphere fall and winter 2017-18, a weak La Niña is favored in the model averages of the IRI/CPC plume [Fig. 6] and also in the North American Multi-Model Ensemble (NMME) [Fig. 7]. The consensus of forecasters is for the event to continue through approximately February-April 2018. In summary, La Niña conditions are predicted to continue (~65-75% chance) at least through the Northern Hemisphere winter (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period). "

So for all of you affected by La Niña events, the next question is to figure out exactly what do La Niña event actually does to your location. There was a time when La Niñas caused drought in the Western United States. However, between the fact that last year as also a La Niña and the current forecast for the rest of November, I decided to clean the storm drains this afternoon. Alas, of course they needed more cleaning than I had hoped. When it comes to home maintenance, the work is never done . . . .

The summary reads: "La Niña is likely (exceeding ~80%) through the Northern Hemisphere winter 2017-18, with a transition to ENSO-neutral most likely during the mid-to-late spring."

The key points of discussion can be summarized as follows:

"La Niña strengthened during the past month, as indicated by an increasingly prominent pattern of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean

. . . .

La Niña is predicted to persist through the Northern Hemisphere winter 2017-18 by nearly all models in the IRI/CPC plume and in the North American Multi-Model Ensemble (NMME).

. . . .

La Niña is anticipated to affect temperature and precipitation across the United States during the upcoming months (the 3-month seasonal temperature and precipitation outlooks will be updated on Thursday December 21st). The outlooks generally favor above-average temperatures and below-median precipitation across the southern tier of the United States, and below-average temperatures and above-median precipitation across the northern tier of the United States."

The expected effects of La Niña leave the center of the United States up for grabs. Last year there is no doubt that rainfall was much above average for the Northern 1/2 of the Western United States. Thus far, we are looking at drought conditions for all of the Western United States as far North as Washington state. Alas, La Niña is Spanish for "the little girl," so I suppose we can only expect this weather phenomena to be "fickle." . . . . . .

As you may remember the sea surface temperatures were supposed to return to neutral in the March-May time frame. Well, here we are in April and the latest report announces:

Quote

During March 2018, La Niña continued to weaken, but was still reflected by below-average sea surface temperatures (SSTs) across the east-central and eastern equatorial Pacific Ocean [Fig. 1].

Nonetheless, the forecasters are sticking to their guns:

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Most models in the IRI/CPC plume predict La Niña will decay and return to ENSO-neutral during the current March-May season [Fig. 6]. The forecaster consensus similarly favors a transition to neutral, with a continuation of ENSO-neutral conditions through the summer 2018.

Beyond that, well there isn't nearly as much enthusiasm to predict the future:

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Thereafter, there is considerable forecast uncertainty, in part due to the lower prediction skill for forecasts made at this time of year.

"Nonetheless, the forecasters are sticking to their guns" How can you be "consistent" if you keep changing your mind(s)?! If they pict the right forecast, they are bound to be correct, someday! For me, if I have a chance to change my mind, I usually do it right before my current opinion is confirmed!!

The critical bit of data is (once more I quote:) "During April 2018, the tropical Pacific returned to ENSO-neutral, as indicated by mostly near-to- below average sea surface temperatures (SSTs) along the equator."

However, just when you thought you could relax because things were back to "normal," the discussion goes on to say: "The majority of models in the IRI/CPC plume predict ENSO-neutral to continue at least through the Northern Hemisphere summer 2018. As the fall and winter approaches, many models indicate an increasing chance for El Niño. Therefore, the forecaster consensus hedges in the direction of El Niño as the winter approaches, but given the considerable uncertainty in ENSO forecasts made at this time of year, the probabilities for El Niño are below 50%. In summary, ENSO-neutral is favored through September-November 2018, with the possibility of El Niño nearing 50% by Northern Hemisphere winter 2018-19 . . . . ."

. . . . . So continues the El Niño or a La Niña soap opera for 2018 with every hope for a brand new season of foolishness for 2018-19!! . . . .